Radiographic films are those intended to be imagewise exposed to X-radiation. The films contain on one or both sides of a film support a silver halide emulsion that, when imagewise exposed and processed, is capable of creating a visible image in the form of developed silver.
It is the prevailing practice to process radiographic films in 90 seconds or less. For example, the Kodak X-OMAT 480 RA .TM. rapid access processor employs the following processing cycle:
Development 24 seconds at 35.degree. C. PA1 Fixing 20 seconds at 35.degree. C. PA1 Washing 20 seconds at 35.degree. C. PA1 Drying 20 seconds at 65.degree. C. PA1 Hydroquinone 30 g PA1 Phenidone .TM. 1.5 g PA1 KOH 21 g PA1 NaHCO.sub.3 7.5 g PA1 K.sub.2 SO.sub.3 44.2 g PA1 Na.sub.2 S.sub.2 O.sub.3 12.6 g PA1 NaBr 35.0 g PA1 5-Methylbenzotriazole 0.06 g PA1 Glutaraldehyde 4.9 g PA1 Water to 1 liter/pH 10.0 PA1 Ammonium thiosulfate, 60% 260.0 g PA1 Sodium bisulfite 180.0 g PA1 Boric acid 25.0 g PA1 Acetic acid 10.0 g PA1 Water to 1 liter/pH 3.9-4.5
with 6 seconds being taken up in film transport between processing steps.
A typical developer (hereinafter referred to as Developer A) exhibits the following composition:
A typical fixer exhibits the following composition:
Radiographic film processors such as RA 480 are capable of exposing large amounts of film over extended periods of time (e.g., a month or more) before its processing solutions are drained and replaced. Extended use of the processing solutions is made possible by the addition of developer and fixer replenishers to compensate for developer and fixer losses by evaporation and film pick up.
One problem that results from the extensive use of processing solutions is often the build up of oily deposits and/or particulates that float to the surface of the processing solutions. These build ups occur when the processor has been allowed to stand idle for an extended period--e.g., overnight or over a weekend.
One solution is to use the first radiographic film run through the processor on start up each morning as a cleaning element. In other words, the film is used to scavenge the unwanted build up in the processing solutions and is discarded after it leaves the processor.
This has been recognized to waste valuable silver contained in the radiographic element that is discarded. Therefore cleaning elements have been offered for sale that contain only a hydrophilic colloid coated on a film support. This approach works on simple processors, but not those that rely on sensors to detect the presence of radiographic film to turn on and turn off the processor. Typically turn on and turn off is controlled by infrared sensors, which cannot detect a cleaning element containing only a hydrophilic colloid coating.
Another problem that is encountered using cleaning elements (or radiographic film that is used for the same purpose) is that the processor operator has no way of knowing whether a particular element has been previously used. Thus, there is a risk that previously used cleaning element in being used once or perhaps several times previously will not be fully effective in cleaning the processing solutions.
Harada et al U.S. Pat. No. 5,260,178 has noted that if the silver halide coating coverage of a radiographic element is quite low, it is impossible for sensors that rely on the attenuation of near infrared sensor beams by silver halide grains to sense the presence of the film in the processor. Hence replenishers are not automatically added to the processing solutions, and the useful life of the processing solutions is markedly decreased. To overcome this problem Harada et al suggested adding to radiographic elements having low silver halide coating coverages an aggregated tricarbocyanine dye having at least two acidic (e.g., sulfonic acid or carboxylic acid) substituents and an absorption peak that is bathochromically shifted by at least 50 nm when aggregated as compared to its absorption in solution. The dye as aggregated in the radiographic film attenuates the infrared sensor beam to provide the necessary signal to turn on the processor. However, once the dye has entered the processing solution (as is insured by the presence of the acidic groups and limiting other substituents), it is no longer capable of attenuating the infrared sensor beam. Instead developed silver is used to control processor shut off. When the beam of the sensor controlling shut off ceases to be attenuated by developed silver, thereby indicating the film has passed through the processor, the processor is automatically turned off.